什么是钠电池的高低温循环测试？

What is the high and low temperature cycling test for sodium-ion batteries?

高低温循环为 UN38.3 T2 项，模拟海陆长途运输、仓储极端温差环境，验证电池密封、电极界面、内部材料耐温稳定性。标准试验流程：样品先在 75℃高温仓静置 4 小时，随后 1 小时匀速降温至 - 40℃低温区保温 4 小时，再升温回到常温，完整流程记 1 个循环，连续重复 10 轮总计 80 小时温变考验。剧烈冷热交替会造成壳体、密封胶、铝塑膜反复热胀冷缩，易诱发封边开裂、微量水汽渗入；同时电极 SEI/CEI 膜、钠盐电解液在极端温度下易发生副反应，造成电压不可逆下跌。合格判定标准：10 轮循环全程无起火、不漏液、无明显鼓包；测试结束常温静置 2 小时复测静态电压，单次电压下降不超过 0.03V，拆解后内部极片无粉化、隔膜无破损。户储、光伏户外场景配套钠电池需额外加长循环次数，高低温循环不合格产品长期户外使用会快速自放电、容量大幅衰减，丧失使用价值。

High-low temperature cycling is Item T2 of UN38.3, simulating extreme temperature difference during long-distance land & sea transportation and storage to verify temperature resistance of battery seals, electrode interfaces and internal materials. Standard procedure: hold samples at 75℃ for 4 hours, cool uniformly to -40℃ within 1 hour and dwell another 4 hours, then heat back to room temperature as one full cycle, repeat 10 times for total 80 hours of temperature variation. Seals, rubber strips and aluminum plastic films expand and contract repeatedly under drastic temperature alternation, easily triggering seal cracking and moisture infiltration. Meanwhile, electrode SEI/CEI films and sodium electrolytes tend to generate side reactions under extreme temperatures, leading to irreversible voltage drop. Pass criteria: no fire, leakage or obvious swelling throughout 10 cycles; static voltage drop less than 0.03V after 2-hour room-temperature recovery, with no powdering electrodes or damaged separators after disassembly. Sodium batteries for household and outdoor photovoltaic storage require extended cycles. Products failing this test suffer severe self-discharge and rapid capacity fading during long-term outdoor service and lose practical value.